1. Assoc. Prof., Dept. of Constr. Engrg., Nat. Taiwan Univ. of Sci. and Technol., P.O. Box 90-130, Taipei, Taiwan 10672, Republic of China.
2. Master, Dept. of Constr. Engrg., Nat. Taiwan Univ. of Sci. and Technol., P.O. Box 90-130, Taipei, Taiwan 10672, Republic of China.